Experimental Study On Electrochemical Oxidation Of Landfill Concentrated Leachate Combined With Fly Ash Dechlorination

With the rapid development of China’s economy and urbanization,the production of domestic waste is growing at a high rate,and waste incineration has become one of the main disposal means for domestic waste in China.The production of concentrated leachate and fly ash from waste incineration has been increasing year by year,and how to dispose of these two waste incineration by-products is one of the hot spots in the waste incineration industry.The recharge method commonly used to treat concentrated leachate can lead to pollution hazards such as increased salinity in landfills,and dechlorination has become a key pre-treatment step in the existing fly ash resource utilization,but the traditional water washing process requires a large amount of water consumption.In this paper,based on the basic physical and chemical characteristics of concentrated leachate and waste incineration fly ash,electrochemical oxidation technology is proposed to achieve organic matter degradation in concentrated leachate and dechlorination of waste incineration fly ash,so that chlorine in fly ash is dissolved in the liquid phase and then anodized to produce active chlorine,which degrades large organic pollutants with poor biochemical properties in concentrated leachate.In this paper,we investigated the effect of removing COD,ammonia nitrogen and chromaticity related indexes from concentrated leachate and dechlorination effect of incinerated fly ash in the mixed system,and also explored the degradation mechanism of mixed electrolytic disposal of concentrated leachate and fly ash.The main experimental results obtained are as follows.1.Electrochemical oxidation has a good effect on the disposal of concentrated leachate.The current density of 75 m A-cm-2 was selected,and the removal rates of COD,ammonia nitrogen and chromaticity of concentrated leachate were 92.1%,90.3%and 98.1% respectively under 180 minutes of electrolysis treatment with slightly increased voltage,and the effluent after electrolysis could meet the subsequent biochemical treatment requirements.2.The mixed electrochemical oxidation of incineration fly ash and concentrated leachate can improve the disposal effect of concentrated leachate and achieve the dechlorination of fly ash at the same time.The removal rates of COD and ammonia nitrogen of concentrated leachate were increased by 36.5% and 53.4% under 120 minutes of electrolytic treatment,and the removal rate of color was increased by 32.1%under 30 minutes of mixed electrolytic treatment.The time after the COD,ammonia nitrogen and chromaticity of the concentrated leachate all reached the standard was reduced by 33.3% compared with the separate electrolysis.The energy consumption using electrochemical oxidation of mixed fly ash was significantly reduced by about46% compared to direct electrolysis at 180 minutes of electrolytic treatment.In addition,the mixed electrochemical oxidation of incineration fly ash and concentrated leachate had some effect on the removal of heavy metals from the concentrated leachate,and the removal rates of Cu,Zn,and Pb heavy metal elements were 91.7%,91.6%,and 95.6%,respectively.3.In the mixed electrochemical oxidation of incineration fly ash and concentrated leachate,the dechlorination effect of incineration fly ash was good,and the efficiency was improved by 20.3%～57.7% compared with the conventional water washing dechlorination.Enhanced removal of organic pollutants from the leachate was demonstrated by adding chloride ions to the electrolysis process of the separate leachate by leaching of chloride ions from the fly ash.The leaching toxic concentrations of Cu,Zn,Pb,Be,and As elements in the fly ash decreased significantly after disposal,with average removal rates of 23.55%,17.96%,37.57%,53.94%,and 62.11%,respectively.The electrolytic disposal of concentrated leachate from external fly ash can effectively improve dechlorination and can be used as a pre-treatment for the subsequent environmentally sound resource-based disposal of fly ash.4.The influence of relevant factors on the overall performance of the system in the mixed electrochemical oxidation experiments of incinerated fly ash and concentrated leachate was investigated.The electrode materials were selected as titanium-rutheniumiridium electrode and porous carbon felt,and the solid-liquid mixture without separation,magnetic stirring and no aeration were used.A current density of 50 m Acm-2 and a solid-liquid ratio of 0.25 g/ m L were selected to maximize the fly ash dechlorination effect per unit of concentrated leachate under 180 minutes of electrolytic treatment,and the final COD degradation efficiency was 92%.This paper provides theoretical guidance and technical support for the co-disposal of concentrated leachate and incineration fly ash by using electrochemical oxidation to simultaneously remove organic pollutants from concentrated leachate and dechlorinate incineration fly ash.